Loudspeaker arrangement



Jan. 3l, 1939. w. scHENKE-r A1.` 2,145,318

IJOUDSPEAKER- RRANGEMENT y I med July 1o, 1937 ATTORNEY v N WALT R A` "Patented Jan. 31, 1939 UNITED STATES PATENT OFFICE LOUDSPEAKER ARRANGEMENT Application July 10, V1937, Serial No. 152,916

In Germany July 14, 1936 3 Claims.

The invention relates to a loudspeaker arrangement in which the individual loudspeakers are equipped with sound conducting surfaces. With the arrangement there is obtained a preferably 5 longitudinally extended characteristic of the sound distribution in the direction of the axis of the loudspeakers, while approximately at right angle to the main axis of the loudspeakers sound should pass at a possibly low degree.

It is known to impart to loudspeakers having large surface diaphragms a certain directive effect by attaching to the loudspeakers cone-shaped sound guides.` If the sound should be radiated preferably only in two directions for instance in 15 the same axis, two loudspeakers are set up of which the one radiates towards the one direction and the-other loudspeaker towards the other direction.

Now it was found in such arrangements that, 2@ especially when transmitting orders or commands, the low frequencies propagating spherically are noticed also outside the main direction of radiation of the loudspeaker, so that desirable silent zones cannot be established, for instance when my, speaking in long halls, on station platforms, etc.

In accordance with the invention a more favorable reproduction with large surface diaphragm loudspeakers equipped with sound guide, for instance in the form of a cone and radiating in 9,@ opposite directions, is obtained in-that the two systems are accommodated within a common housing.

The air space enclosed in the housing causes a damping of the large amplitudes of the diam phragm and therefore predominantly a damping of the low frequencies.

In this way the propagation of the low frequencies particularly in the directions at right angle to the main direction of radiation will be reduced.

m Laterally to the main direction, silent zones are obtained in which the sound is greatly reduced so that disturbances cannot occur.

The directional characteristic of the loudspeakers has the shape of an 8 in this arrangement.

,w The constricted part of the directional characteristic lies practically on the center line between both loudspeakers. With such a characteristic of the loudspeaker arrangement it is now possible to set up a microphone in the direct vicinity of the 5U loudspeakers in the direction at right angle to the main direction of radiation without acoustic feed back taking place between the microphone and the loudspeakers.

The elongated characteristic is of particular importance to the transmission of orders in stadiums, on station platforms, in long halls, etc., in order to avoid lateral echo andecho-phenomena.

In many cases it may be'necessary to avoid pronounced silent Zones at right angle to the main radiation. In accordance with a further E development of the loudspeaker arrangement according to the invention, measures are taken whereby the air enclosed in the housing of the loudspeaker arrangement can communicate with the outer air. It is advisable to provide openings w in the walls of the housing whereby the sizeof said openings is possibly controllable, or else, shutter-like arrangements are built into the walls so as `to obtain a greater or lesser couplingv of the interior space with the outer air. Eventually, w the walls not having loudspeakers fastened thereto may also additionally be adapted to open up or may open up as such.

With these arrangements the characteristic of the loudspeaker will be modified such that the @il 8like shape will be widened out in the center so that an elongated characteristic will be obtained. This entails the advantage that the transmission can be properly heard directly underneath the loudspeaker and in its vicinity. These control g5 arrangements at the housing have the further advantage that the range of the sound waves can be influenced.

The loudspeaker arrangement can be so operated that when using for instance two loudao speakers the diaphragms of the loudspeakers move both simultaneously outwards with respect to the housing. In order to obtain especially sharp extinction zones, the loudspeakers can be so connected that one of the loudspeaker diaphragms gg moves inwards while at the same moment the other loudspeaker diaphragm moves outwards. With these different types of operation the range and the sound distribution of the sound waves can be iniiuenced in wide limits.

In placevof a single loudspeaker, several loudspeakers may operate on one or several coneshaped sound guide surfaces in the same direction.

The figures show an example of construction of dt the loudspeaker arrangement in accordance with the invention.

Figures 1, 2 and 3 show bottom, side (partly in section) and end (partly in section) views,

respectively, of an embodiment according to the ao invention. Figure 4 represents directional characteristics of the loudspeaker arrangement according to the invention, and Figure 5 represents one of the possibilities of applying the loudspeaker arrangement according to the invention. an

In a housing I (Figures 1 to 3) the loudspeakers 5 and 6 are arranged in the obliquely disposed walls 3 and 4. Cone-shaped sound guides I and 8 are disposed in front of these loudspeakers having large surface diaphragms. The length o! the sound guides corresponds approximately to the length of the ordinary sound Walls. The sound guides 'I and 8 are likewise disposed obliquely downwards. The loudspeaker and eventually the sound guides may however also be arranged in the same axis.

In the bottom 9 of the housing I one or more slots I IJ are provided which can be covered up to a greater' or lesser degree by movable plates or bars II.- In place of the slots to be covered also other means may be used, for instance, displaceable shutters, slides, or the like. Furthermore, also the side walls I2 and I3 may beopened up t0 a greater or lesser degree independently of each other. At the top of the housing a hook I4 is arranged from which the loudspeaker arrangementv con be suspended, or a hole may be provided in the bottom 9 of the housing I through which a mast may be inserted so that the loudspeaker can be supported from the ground.

Figure 4 shows directional characteristics of a loudspeaker arrangement according to the invention. The curve I6 at the loudspeaker arrangement I5 shows schematically the characteristic for an entirely closing housing. At the constricted place of the characteristic IS a microphone may be set up for instance at the place I'I.

When opening the slots I0, or the side walls I2 and I3 the characteristic can be varied to such an extent that for instance the characteristic I8 is obtained.

Figure 5 shows the use oi the loudspeaker according to the invention, for instance over oblique terrain such as found in open air stages or other arrangements. By opening up the side walls I2 and I3 the radiation cone of the loudspeaker arrangement can be influenced, and it is possible in this manner so to adjust the sound energies radiated by the loudspeaker that the field covered by this loudspeaker will not be disturbed by other loudspeakers set up in the adjacent field. The lines I9 and 20 show, for instance, the radiation cone at right angle to the direction of the axis of the loudspeaker belonging to the loudspeaker arrangement when set up on an oblique line 2|. In the example of construction the walls I2 and I3 are opened up at different degrees.

What we claim is:

l. A loudspeaker system for controlling the directional radiation characteristic thereof, comprising an enclosure provided with upper and lower walls, a pair of oppositely disposed side walls which are inclined downwardly and which have each a central aperture therein, and a second pair of oppositely disposed side walls which are hinged at their upper edges, a pair of loudspeakers arranged within the enclosure with each loudspeaker diaphragm mounted on its respective apertured side wall to permit the sound therefrom to radiate in substantially opposite directions, and a horn member mounted on each apertured side wall external of the enclosure, the hinged side walls adapted to be separately adjustable whereby the space within the enclosure may be made to communicate with the outside air to a greater or less degree.

2. A loudspeaker system for controlling the directional radiation characteristic thereof, comprising a pair of loudspeakers disposed to radiate in substantially opposite directions, a common enclosure for said loudspeakers, a cone-shaped sound guide associated with each of said speakers,l and adjustable apertures provided in the common enclosure, the extent to which the apertures are opened determining the amount of radiation in a direction at right angles to the main direction of radiation.

3. A loudspeaker system according to claim 2, wherein the common enclosure is provided with adjustable side walls whereby the space within the enclosure may be made to communicate with the outside air to a greater or less degree.

WALTER SCHENK. WALDEMAR MARTHIENS.

CII 

